1. Field of the Invention
The present invention generally relates to a liquid-firing head and a manufacturing method thereof, and, an ink-jet recording device and a micro-actuator.
2. Description of the Related Art
In general, an electrostatic ink-jet head, which is one of liquid-firing heads, is used in an ink-jet recording device used as an image recording/forming device of a printer, a facsimile machine, a copier, a plotter and so forth. The electrostatic ink-jet head includes a nozzle firing an ink drop, a liquid chamber (which may also be referred to as an ink flow path, a pressurizing chamber, a firing chamber, a pressure chamber, a pressurizing liquid chamber, or the like) communicating with the nozzle, a vibration plate which is used as a wall of the liquid chamber, and an electrode facing the vibration plate. Then, as a result of a voltage being applied between the vibration plate and electrode, an electrostatic force is generated, which deforms the vibration plate so that the pressure/volume in the liquid chamber is changed. As a result, an ink drop is fired via the nozzle. A part of this ink-jet head including the vibration plate and electrode is called a micro-actuator. The micro-actuator may also be used as a micro-pump or the like.
Japanese Laid-Open Patent Application No. 6-71882discloses such an electrostatic ink-jet head. In this ink-jet head, the vibration plate which is used as a wall of the liquid chamber and the electrode are disposed in parallel with one another. A gap formed thereby is called xe2x80x98a parallel gapxe2x80x99.
Further, Japanese Laid-Open Patent Application No. 9-39235 discloses an electrostatic ink-jet head in which a length of a gap formed between the vibration plate and electrode varies stepwise as a result of the electrode being disposed stepwise. Furthermore, Japanese Laid-Open Patent Application No. 9-193375 discloses such an electrostatic ink-jet head that, as a result of the electrode being disposed obliquely with respect to the vibration plate, a sectional shape of the gap formed between the vibration plate and electrode is such that a surface on the vibration plate and a surface on the electrode are not parallel at least at a part thereof (such a gap is called xe2x80x98non-parallel gapxe2x80x99).
In such an electrostatic ink-jet head (also in a micro-actuator), it is necessary to form the gap between the vibration plate and electrode at a high accuracy. For this purpose, an oxide film is formed on a silicon substrate, or an insulating substrate such as a Pyrex glass is used, a groove for forming an electrode having a predetermined depth is formed into the oxide film or insulating substrate, and an electrode having a predetermined thickness is formed on a bottom surface of the groove. Thereby, as a result of utilizing the part of the oxide film or insulating substrate other than the groove as a gap spacer for determining the gap between the vibration plate and electrode, it is possible to obtain a predetermined gap length between the vibration plate and electrode.
However, in such an electrostatic ink-jet head in the related art, when the above-mentioned parallel gap is formed, the gap length (the distance between the surface of the vibration plate and the surface of the electrode) may vary, due to variation in depth of the groove for forming the electrode (variation in height of the gap spacer), variation in thickness of the electrode, and also, variation in thickness of a protection insulating film if this film is formed on the surface of the electrode. Also, it is difficult to further reduce the size of the gap.
Further, if the non-parallel gap is formed, especially if the non-parallel gap starting from a position at which the gap length of 0 is formed, a groove having a shape of the non-parallel gap should be formed in a silicon substrate, and an electrode should be formed in the groove. Accordingly, an end of the electrode or an end of a protection insulating film formed on the surface of the electrode may project from or may be lower than the top surface of the silicon substrate (the top surface of the gap spacer). Thereby, unevenness occurs on the surface of the silicon substrate.
In such a case, it may be difficult to bond the thus-formed part with a substrate in which a vibration plate is provided, or, even when the bonding may be achieved, such a large amount of polishing is needed for enabling the bonding that variation in gap length increases.
When variation in gap length thus increases, it may result in variation in firing performance of the resulting ink-jet head such as ink-drop firing volume, ink-drop firing speed and so forth, variation in position at which fired ink reaches, degradation in image quality obtained through printing by using the ink-jet head, and so forth.
The present invention has been devised in consideration of the above-mentioned problems, and, an object of the present invention is to provide a liquid-firing head in which gap accuracy is improved, a method of manufacturing it, an ink-jet recording device in which image quality of recorded image is improved, and a micro-actuator in which the gap accuracy is improved.
A liquid-firing head according to the present invention comprises:
a nozzle firing a liquid drop;
a liquid chamber communicating with the nozzle;
a vibration plate which acts as a wall of the liquid chamber; and
an electrode facing the vibration plate, and
wherein the vibration plate is deformed by an electrostatic force, and, thereby, the liquid drop is fired through the nozzle, and
wherein a groove for forming a gap between the electrode and the vibration plate is formed in the electrode.
Thereby, it is possible to form the gap at a high accuracy, and to improve the ink-drop firing performance.
In this configuration, it is preferable that the electrode comprises a polysilicon layer. Thereby, it is possible to easily form the high-accuracy gap.
A liquid-firing head according to another aspect of the present invention comprises:
a nozzle firing a liquid drop;
a liquid chamber communicating with the nozzle;
a vibration plate which acts as a wall of the liquid chamber; and
an electrode facing the vibration plate, and
wherein the vibration plate is deformed by an electrostatic force, and, thereby, the liquid drop is fired through the nozzle, and
wherein a groove for forming a gap between a protection insulating film, formed on the electrode, and the vibration plate is formed in the protection insulating film.
Thereby, controllability of the gap is improved, and the process yield increases.
In this configuration, the electrode may comprise one of a polysilicon layer, a tungsten silicide layer, a titan silicide layer, and a laminated layer thereof. Thereby, it is possible to easily form the protection insulating film.
Further, the protection insulating film may comprise one of a polysilicon oxide film or a high-temperature oxide film. Thereby, the reliability is improved, and degradation of the electric performance is reduced.
A liquid-firing head according to another aspect of the present invention comprises:
a nozzle firing a liquid drop;
a liquid chamber communicating with the nozzle;
a vibration plate which acts as a wall of the liquid chamber; and
an electrode facing the vibration plate, and
wherein the vibration plate is deformed by an electrostatic force, and, thereby, the liquid drop is fired through the nozzle, and
wherein:
a gap spacer part determining a gap between the vibration plate and the electrode comprises the same layer as that of the electrode; and
a groove for forming the gap between the electrode and the vibration plate is formed in the electrode.
Thereby, the gap accuracy is improved, the liquid-firing performance is improved, a high-accuracy gap can be formed with higher process yield, and, in particular, a high-accuracy non-parallel gap can be easily formed.
In this configuration, by employing a polysilicon layer for the electrode, it is possible to easily form the high-accuracy gap.
A liquid-firing head according to another aspect of the present invention comprises:
a nozzle firing a liquid drop;
a liquid chamber communicating with the nozzle;
a vibration plate which acts as a wall of the liquid chamber; and
an electrode facing the vibration plate, and
wherein the vibration plate is deformed by an electrostatic force, and, thereby, the liquid drop is fired through the nozzle, and
wherein:
a groove for forming a gap between the electrode and the vibration plate is formed in the electrode; and
a part of the electrode is used as a gap spacer part determining the gap between the electrode and the vibration plate.
Thereby, it is possible to form a higher-accuracy gap, and the liquid-drop firing performance is improved.
In this configuration, by employing a polysilicon layer for the electrode, it is possible to easily form the high-accuracy gap.
In any of the above-mentioned configurations, the gap formed by the groove of the electrode may have an inclined surface providing a part at which a gap length is zero.
Thereby, it is possible to improve an effect of reducing the driving voltage and the liquid-drop firing performance.
A liquid-firing head according to another aspect of the present invention comprises:
a nozzle firing a liquid drop;
a liquid chamber communicating with the nozzle;
a vibration plate which acts as a wall of the liquid chamber; and
an electrode facing the vibration plate, and
wherein the vibration plate is deformed by an electrostatic force, and, thereby, the liquid drop is fired through the nozzle, and
wherein:
the electrode has a protection insulating film on a surface thereof;
a gap spacer part determining a gap between the vibration plate and the electrode is formed of the laminated film same as the electrode and the protection insulating film; and
a groove for forming the gap between the vibration plate and the protection insulating film is formed in the protection insulating film.
Thereby, the gap accuracy is improved, the liquid-firing performance is improved, a high-accuracy gap can be formed with higher process yield, and, in particular, a high-accuracy non-parallel gap can be easily formed.
A liquid-firing head according to another aspect of the present invention comprises:
a nozzle firing a liquid drop;
a liquid chamber communicating with the nozzle;
a vibration plate which acts as a wall of the liquid chamber; and
an electrode facing the vibration plate, and
wherein the vibration plate is deformed by an electrostatic force, and, thereby, the liquid drop is fired through the nozzle, and
wherein:
the electrode has a protection insulating film on a surface thereof;
a groove for forming the gap between the vibration plate and the protection insulating film is formed in the protection insulating film; and
a part of the electrode and the protection insulating film is used as a gap spacer part determining the gap between the vibration plate and the protection insulating film.
Thereby, the gap accuracy is improved, the liquid-firing performance is improved, a high-accuracy gap can be formed with higher process yield, and, in particular, a high-accuracy non-parallel gap can be easily formed.
In any of the above-mentioned configurations, the electrode may comprise one of a polysilicon layer, a tungsten silicide layer, a titan silicide layer, and a laminated layer thereof. Thereby, it is possible to easily form the protection insulating film. Further, the protection insulating film may comprise one of a polysilicon oxide film or a high-temperature oxide film. Thereby, the reliability is improved, and degradation in the electric performance is reduced. Furthermore, the protection insulating film may also be formed on a side surface of the electrode. Thereby, the reliability of the device is improved.
Further, the protection insulating film may fill each separating region formed between the particular electrodes. Thereby, a polishing process or a process of forming a gradation pattern can be performed after dividing the electrode into the particular ones. Accordingly, flexibility in process is improved. Further, the gap formed by the groove of the protection insulating film may have an inclined surface providing a part at which a gap length is zero. Thereby, an effect of reducing the driving voltage and the liquid-drop firing performance can be improved. Furthermore, the groove may be formed after the electrode is divided into particular electrodes, the protection insulating film fills a separating region between the particular electrodes, and the surface of the protection insulating film is polished. Thereby, the gap accuracy is improved.
Further, in any of the above-mentioned configurations, the surface of the gap spacer part may be mirror-polished so as to have a surface morphology not larger than 1 nm. Thereby, it is possible to render silicon direct bonding with high reliability in the bonding. Furthermore, the periphery of the gap may be sealed. Thereby, it is possible to easily prevent water or the like from entering the gap when the wafer is divided into particular chips. In this case, a measure enabling the inner pressure of the gap to be opened to the atmospheric pressure during manufacture thereof may be provided. Thereby, it is possible to reduce variable variations in resulting performance, and to improve the firing efficiency. In this case, a communicating path enabling the gap to communicate with the atmosphere may be provided in a region other than an electrode drawing part for externally drawing the electrode. Thereby, it is possible to easily open the gap to the atmosphere while preventing water or the like from entering the gap
A method of manufacturing a liquid-firing head according to the present invention having the groove formed in the electrode, comprising the steps of:
a) polishing the surface of the electrode; and
b) forming the groove after the step a).
Thereby, variation in gap (size/shape) is reduced, and, a high-accuracy gap with little variation, that is, uniform, can be formed.
A method of manufacturing another liquid-firing head according to the present invention having the groove formed in the protection insulating film, comprising the steps of:
a) polishing the surface of the protection insulating film; and
b) forming the groove after the step a).
Thereby, variation in gap is reduced, and, a high-accuracy gap with little variation can be formed.
Another method of manufacturing a liquid-firing head according to the present invention having the groove formed in the electrode, comprising the steps of:
a) forming the grooves in the electrode; and
b) dividing the electrode to particular electrodes after the step a).
Thereby, variation in gap is reduced, and, a high-accuracy gap with little variation can be formed.
Another method of manufacturing a liquid-firing head according to the present invention having the groove formed in the protection insulating film, comprising the steps of:
a) forming the grooves in the protection insulating film; and
b) dividing the electrode and the protection insulating film to particular electrodes and protection insulating films after the step a).
Thereby, a non-parallel gap can be formed at a high accuracy.
Another method of manufacturing a liquid-firing head according to the present invention comprising the steps of:
a) dividing the electrode into particular electrodes;
b) filing a separating region between the particular electrodes with the protection insulating film;
c) polishing the surface of the protection insulating film; and
d) forming the groove after the steps a), b) and c).
Thereby, a high-accuracy gap can be formed in a process having improved flexibility.
A method of manufacturing a liquid-firing head according to the present invention in which the periphery of the gap is sealed, comprising the step of opening the inner pressure of the gap to the atmospheric pressure during manufacture thereof. Thereby, it is possible to reduce various problematic variations in resulting performance. In this case, the step of opening the inner pressure of the gap to the atmospheric pressure during manufacture thereof through a communicating path provided in a region other than an electrode drawing part for externally drawing the electrode may be included. Thereby, it is possible to easily open the gap to the atmosphere while preventing water or the like from entering the gap.
An ink-jet recording device according to the present invention comprising an ink-jet head for firing an ink drop, wherein the ink-jet head comprises a liquid-firing head according to the present invention described above, or is manufactured by a method according to the present invention described above. Thereby, the ink-drop firing performance, and ink-drop reaching position accuracy are improved, and, thereby, the image quality of an image printed by the recording device is improved.
A micro-actuator according to the present w invention, comprises:
a vibration plate; and
an electrode facing the vibration plate,
wherein the vibration plate is displaced by an electrostatic force, and
wherein one of the electrode and a protection insulating film formed on the electrode has a gap between the vibration plate and the electrode.
Thereby, it is possible to form a high-accuracy gap, and, thereby, improve the operation performance of the actuator.
A micro-actuator according to another aspect of the present invention, comprises:
a vibration plate; and
an electrode facing the vibration plate,
wherein the vibration plate is displaced by an electrostatic force, and
wherein a gap spacer part determining a gap between the vibration and the electrode comprises the same layer as one of the electrode and the electrode with a protection insulating film.
Thereby, it is possible to form a high-accuracy gap, and, thereby, improve the operation performance of the actuator. Furthermore, a high-accuracy gap can be formed with high process yield, and, in particular, a high-accuracy non-parallel gap can be easily formed.
Other objects and further features of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.